we just released our free CoAP stack ("lobaro-coap") to the esp8266 platform.Our CoAP implementation was primary designed for embedded hardware platforms and easy usage.

Features are:* easy to use “C” CoAP stack* open source (MIT)* complete request/response logic* complete retry logic* piggybacked & separate reponses* prepared for sleeping server* runs on static memory are with own memory allocator* no need for FreeRTOS SDK (but should be no problem)* only one UDP socket internally used* wifi credentials can be set via CoAP on esp8266 softAP interface

Documentation

About Us

Espressif Systems is a fabless semiconductor company providing cutting-edge low power WiFi SoCs and wireless solutions for wireless communications and Internet of Things applications. We are the manufacturer of ESP8266EX.